Problem: Solve for $z$ : $-28 = 30 + z$
Explanation: Subtract $30$ from both sides: $ \begin{eqnarray} \\ \hphantom{-28 {- 30}} &\hphantom{=}& \hphantom{z} \\ -28 &=& 30 + z \\ \\ {-30} && {-30} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ -28 {- 30} &=& z \\ \end{eqnarray} $ Simplify. $ z = -58$